Touchscreens are becoming increasingly common as user interfaces in many electronic devices such as mobile phones, tablets and portable computers. One current touchscreen technology comprises a transparent electronic touch sensitive layer which is overlaid on a rigid electronic display panel and which can directly sense the touch of a physical pointer such as a finger or stylus.
A touchscreen can support richer user interaction if it can sense the presence of a physical pointer that is close to, but not actually in contact with, the touchscreen. Such interaction may include detecting a so-called “hover” state of the pointer, as described below. In order to do so, however, and because the pointer is not in contact with an electronic sensing layer, the system must incorporate additional sensors able to remotely detect the pointer. Various parties have designed and built such non-conventional touchscreen systems, referred to hereinafter as augmented touchscreen systems.
One current augmented touchscreen system comprises a camera having a field of view looking generally across a surface, where the images from the camera are analysed to detect a pointer and the pointer's reflection in the surface. Such systems require that the surface be sufficiently reflective to allow the pointer's reflection to be detected by the camera. If the pointer and its reflection meet in the image, the pointer is deemed to be touching the surface. If there is a gap between the pointer and its reflection captured in the image, the pointer is deemed to be close to, but not touching, the surface, and this is interpreted as the “hover” state.